The CDC said 162 passengers and 11 crew members reported that they had fallen ill.

The CDC said 162 passengers and 11 crew members reported that they had fallen ill.

Photo: Mayra Beltran, Houston Chronicle

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The cruise line suspects the cause of the outbreak is norovirus.

The cruise line suspects the cause of the outbreak is norovirus.

Photo: Mayra Beltran, Houston Chronicle

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Boatman Mark Henry tosses a mooring line off a bollard ahead of the cruise ship Caribbean Princess' first voyage from the Bayport Cruise Terminal on Nov. 5. The ship is returning early from it's latest trip amid thick fog and an outbreak of norovirus. less

Boatman Mark Henry tosses a mooring line off a bollard ahead of the cruise ship Caribbean Princess' first voyage from the Bayport Cruise Terminal on Nov. 5. The ship is returning early from it's latest ... more

A worker waits to leave on the cruise ship Caribbean Princess from the Bayport Cruise Terminal Nov. 5, 2013 in Pasadena, TX.

A worker waits to leave on the cruise ship Caribbean Princess from the Bayport Cruise Terminal Nov. 5, 2013 in Pasadena, TX.

Photo: Eric Kayne, For The Chornicle

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The new Caribbean Princess departs on its maiden voyage from Port Everglades in Fort Lauderdale, Fla., Saturday, April 3, 2004. | Photo by Andy Newman/Princess Cruises

The new Caribbean Princess departs on its maiden voyage from Port Everglades in Fort Lauderdale, Fla., Saturday, April 3, 2004. | Photo by Andy Newman/Princess Cruises

Photo: ANDY NEWMAN, .

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Cruise ship back in Houston after nearly 200 fall ill

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For the third time in less than a month, federal health officials are investigating an outbreak of illness on a U.S.-based cruise ship after more than 170 passengers and crew members on a Houston-originating vessel reported gastrointestinal symptoms.

The Caribbean Princess arrived at the Bayport Cruise terminal at about 9 p.m. Thursday, more than 24 hours sooner than scheduled. It was previously set for an early arrival on Friday. Centers for Disease Control and Prevention investigators planned to board the vessel for a public health investigation.

The cruise line suspects the cause of the outbreak is norovirus, a highly contagious infection that causes severe vomiting and diarrhea — the predominant symptoms reported by passengers, according to a CDC preliminary report.

Norovirus also was believed to be the cause of a highly publicized outbreak this week that struck Royal Caribbean's Explorer of the Seas. That ship docked Wednesday in New Jersey after an infection spread to roughly 700 people on board.

The Caribbean Princess left the Port of Houston on Jan. 25 bound for the Western Caribbean with more than 4,200 people on board. The vessel was scheduled to return on Saturday.

According to CDC spokesman Llelwyn Grant, 162 of the 3,102 passengers and 11 of the 1,148 crew members had reported illness by late Thursday afternoon. Ship employees implemented some of the agency's recommendations for preventing further infections, he said.

"We have already been working with the crew in getting some stool samples so we can send that back to our labs for testing," Grant added.

The ship's rapid norovirus tests on samples were positive for the infection, according to the CDC.

The public health agency instructed the crew to increase cleaning and disinfection procedures and to notify passengers about the outbreak to encourage reporting.

Caribbean Princess passengers will remain on the ship until they are cleared by U.S. Customs authorities, which will take several hours, according to Princess Cruises spokeswoman Julie Benson.

"They'll be going either home or into hotels," Benson said, adding that none are expected to go to hospitals. "We don't believe anybody will be ill getting off the ship. The ship did a great job stopping the spread of illness. The number of people who were ill continued to decrease dramatically over the last couple of days."

Besides overnight accommodations in Houston, the cruise line said passengers would be offered a 20 percent credit toward a future cruise.

Once on board, CDC investigators will spend several days "basically evaluating the outbreak and trying to look at some of the responsive activities that we recommended to the cruise line folks," Grant said.

Princess Cruises said in a statement Thursday that the trip was cut short by one day because of thick fog expected over the weekend. The statement also revealed that more than 100 people had been treated at the ship's medical center.

"Caribbean Princess has experienced an increase in the number of cases of gastroenteritis among passengers, which has been confirmed to be norovirus," the statement said. "Because of the increased sensitivity surrounding norovirus by both cruise lines and the (CDC) in this winter season, we notified the CDC ...to ensure all appropriate measures are followed for an extensive sanitation of the ship prior to the next cruise departing February 1."

Benson said the ship "will be undergoing a thorough sanitization" before the next cruise, which is scheduled to depart around 4 p.m. Saturday.

Asked if there was enough time to clean up the ship before Saturday afternoon, Benson said: "We have a good history and we have good procedures to do that."

The Caribbean Princess is part of Carnival Corp., a family of brands that include Carnival Cruise Lines, Princess Cruises, Holland America Line and Seabourn in North America.

According to the CDC's vessel sanitation program, the Caribbean Princess outbreak is the third on a U.S.-based cruise ship this year. In 2013, there were nine reported incidents — seven caused by norovirus, one by E. coli and another in November from a still-unknown cause.

In February 2013, an engine fire left the Carnival cruise ship Triumph adrift without power for several days, forcing passengers to endure a lack of air conditioning or, in some case, functioning toilets. The plight of the vessel — which departed from Galveston — drew international attention and became a public relations disaster for the cruise line.

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